The term “order picking” has become associated with systems designed for receiving, storing and delivering product to and from some form of storage area. They may also use some form of warehouse management system for co-ordination of storage.
Products for distribution are often stored in a warehouse and retrieved therefrom for loading onto a vehicle for transport to customers. In an effort to increase the speed and efficiency of the storage and delivery system, apparatus for automated retrieval, or “picking”, of product from the storage space have been developed. This has represented a large advance in the efficiency of order picking systems, which traditionally heavily relied on manual handling. Further advantages of automated systems include reduced overall cost, increased accuracy and decreased risk of personal injury.
An ongoing problem faced by warehouse managers is the efficient use of space within a warehouse. Each square meter of floor space within the warehouse has an associated cost and the warehouse management system must seek to obtain the maximum use of the space in the warehouse to be efficient and competitive.
Picking systems, whether manual or automatic, typically have a defined and fixed “pick face”, or surface from which they can retrieve product. One problem presented to pick systems is how to replenish pick locations once they have been emptied. Traditionally, such replenishment is performed manually, with the assistance of a forklift or similar. This requires access to all parts of the storage area, the access channels, roads or similar requiring valuable space. Another problem faced by pick system designers is how to minimise the distance that the picking means, automated or manual has to travel to fulfill typical orders. The more the picking means has to travel, the longer the picking takes.
Due to demand variations, some products will invariably ship in greater quantities than others. Individual deliveries to customers may consist of relatively large quantities of a few products, but only a few, or even single cases or individual items of other products. This variability of product volumes presents a logistics problem in attempting to use the available resources, whether automated or manual or a combination most efficiently to obtain the best throughput.
Furthermore, the product stored in a warehouse may include a substantial variety of any given product. For example, a warehouse storage for milk will include crates containing cartons or bottles of different capacity, different flavour (e.g. conventional, chocolate, strawberry, banana, etc) and of different constituents or nutritional composition (e.g. full fat, trim, super-trim, skim, high calcium, etc). In addition, the product may be sorted by date of production. Thus, a warehouse may contain a large range of product over a wide area. Selection of the product to fill specific orders is, consequently, a complex process requiring: a) a sophisticated warehouse management system for the location of product delivered and stored, and for the selection of product for an order; and b) an efficient system for access to and removal of product from the storage area to fill an order.
Automated, robotic systems for order picking generally involve an x-y gantry system and a design for picking up individual containers or individual stacks of containers and transporting them from or to a conveyor. In the usual course, orders are delivered on pallets. Thus, the individually collected containers must then be formed into stacks of a required height, the stacks then formed into frames or partial frames of a required width and the frames or partial frames combined to form a pallet unit.
Such systems can be inefficient and/or impractical in a large warehouse environment where orders require product to be collated from many different parts of the warehouse. The robotic pickers have to cover large distances, back and forth, in the warehouse to complete a given order.
An existing automated storage and retrieval system is available from Automated Fork Truck Inc. of Salt Lake City, Utah, United States of America. This system is a storage and retrieval fork system that stores and retrieves product from vertically stacked racks. The system places product into and retrieves product from the racks through a vertical pick face at the end of a number of stacked racks and each rack being more than one pallet deep, with pallets being pushed away from the pick face for storage of another pallet in the same rack. With this system, the number of pick faces is limited and removal of individual containers from within pallets is not facilitated.
U.S. Pat. No. 6,061,607 discloses an order picking system for retrieving high volume and low volume product from two separate regions, but more specifically involves the location of product in vertical stacks in cells of totes. Low demand product is retrieved by a picker mechanism in a pick zone, by movement of that mechanism vertically above the pick zone and selection of individual articles from selected cells in selected totes. The system is primarily directed towards storage and retrieval of individual articles, which may be of high or low demand, rather than of containers containing a plurality of articles, which must, inevitably, be stored and transported in a different way.
U.S. Pat. No. 5,636,966 discloses a case picking system that removes full layers of cases and individual cases from storage towers. The storage towers are replenished from a further tower acting as a replenishment system. This requires double-handling of the transported layers. Moreover, the layers themselves are more demanding in their transport requirements than are individual cases or pallets.
In order to maximise the efficiency of such a system, it is important that the largest “natural unit of handling” be used where ever possible. Typically one “natural unit of handling” may be a full stack of a defined number of containers. A larger natural unit of handing may be a defined number of full stacks, referred to herein as a “frame”. The number of stacks in a frame, and the number of containers in a full stack, may be determined by the physical limitations of the bulk shipping and container handling apparatus. For example, the size of a frame of product, e.g. 6 full stacks, each 6 containers high, may be determined by the maximum number of containers which a specially equipped forklift can carry.
Efficiency within the warehouse is promoted by moving and storing frames of product together wherever possible, and by moving full stacks of product wherever it is not possible to move entire frames, or where less than an entire frame is required.
International Application No. PCT/NZ2002/000008 describes an order picking system whereby product is stored in high, medium and low demand zones, with high demand product being handled in frames, medium demand product being handled in full stacks and low demand product being handled in stacks or partial stacks. This system works well, but may not make optimum use of the space available.
The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in any country.